Ethylenediaminetetraacetic Acid (EDTA)-Decalcified, Formalin-Fixed Paraffin-Embedded (FFPE) Tumor Tissue Shows Comparable Quality and Quantity of DNA to Non-Decalcified Tissue in Next-Generation Sequencing (NGS)

Background: Bone tissue decalcification is essential for histopathological evaluation, but conventional methods using inorganic acids degrade nucleic acids, limiting molecular testing. EDTA is known to better preserve DNA, but its suitability for next-generation sequencing (NGS) in clinical settings remains to be validated. Methods: This retrospective study evaluated 752 formalin-fixed paraffin-embedded (FFPE) tissue samples undergoing NGS between January 2022 and October 2024. Of these, 31 were decalcified using EDTA (Osteosoft, Merck, Germany). DNA was extracted using the Qiagen AllPrep® kit and quantified using Qubit and NanoDrop. Libraries were prepared with a custom 30-gene Ampliseq panel and sequenced on the Ion Torrent platform. Sequencing was deemed suboptimal if <95% of target regions reached ≥250X depth. Results were compared to 721 non-decalcified FFPE samples. Results: Suboptimal sequencing occurred in 9.7% of EDTA-decalcified and 9.0% of non-decalcified cases (p = 0.9). DNA concentration (Qubit) and NanoDrop 260/280 ratios were not significantly different (p = 0.4 and p = 0.8, respectively), though EDTA cases had lower DNA concentrations (NanoDrop, p = 0.006) and 260/230 ratios (p = 0.002). Mutation detection in decalcified samples was consistent with known mutation profiles for respective tumor types. Conclusions: EDTA-decalcified FFPE bone tissues produce NGS results comparable to non-decalcified specimens, with similar sequencing success rates and acceptable DNA quality. These findings support the use of EDTA as a suitable decalcification method for molecular diagnostics, enabling broader inclusion of bone specimens in clinical testing.